Method for producing an anti-wetting barrier, and anode comprising one such anti-wetting barrier

ABSTRACT

The invention concerns a method for producing an anti-wetting barrier ( 1 ) on an electrode ( 2 ) that is connected to the anode body ( 3 ) of an electrolyte condenser, whereby a fluid anti-wetting agent has been applied to the electrode ( 2 ) with drops and whereby the spatial distance (d) of the drops ( 4 ) on the electrode ( 2 ) has been so selected that an anti-wetting barrier ( 1 ) in the form of a continuous line develops after the drying of the anti-wetting agent. The application of the anti-wetting barrier ( 1 ) by drops allows the use of two-dimensional or wire-formed anode diverters. Furthermore, the invention concerns an anode with the anti-wetting barrier ( 1 ).

[0001] The invention concerns a method for producing an anti-wettingbarrier on an electrode that is connected to the anode body of anelectrolyte condenser, in which an anti-wetting agent is applied theelectrode to create the anti-wetting barrier. Furthermore, the inventionconcerns the anode of an electrolyte condenser with an anti-wettingbarrier.

[0002] Electrolyte condensers are, as in this case, tantalum condenserscovering a porous anode body that is connected to an electrode and thatis covered by an electrically conductive layer. The anode body is incontact with the electrode and represents the anode of the electrolytecondenser together with the electrode. On the surface of the porousanode body, a multilayered cathode is produced from conductive materialsduring processing of electrolyte condensers by the following: dipping,drying and pyrolysis processes, one after the other. Wetting theelectrode with used solutions, suspensions, dispersions and lacquers forthe dipping processes must be prevented, because the resulting liquidleft over from this forms a deposit firmly on the electrode. The deposithas the disadvantage of affecting the electrical characteristics ofresulting condensers. Wetting the electrode can, in this case, beachieved from excessive dipping or from a meniscus formation of theliquid used during the dipping process. Additionally, wetting theelectrode can take place using the capillary effect released, in thiscase, by channels on the surface of the electrode.

[0003] Furthermore, firm deposits on the electrode negatively affect thecondensers' space utilization.

[0004] It is therefore an objective to establish an anti-wetting barrieron the electrode that should be placed as closely as possible to ananode body in order to limit and/or prevent the development of furtherdeposits.

[0005] For electrolyte condensers, anti-wetting barriers have been knownto exhibit the form of a round wire connected to the anode body that isitself connected to the electrodes exhibited in the form of a Teflonring spread onto the electrode before the dipping step. Such a Teflonring has the disadvantage that it either must be reapplied to theelectrode after the dipping step or it stresses, in this case it remainson the electrode, much of the area and thus depletes the condenser'sstorage utilization that has usually been produced for chip condensers.

[0006] Furthermore, a method is known in the prior art, in which theround-wire formed electrode is placed in a continuous stream of fluidanti-wetting agent. With this, an anti-wetting barrier forms on theelectrode when the anti-wetting agent dries out. This method has thedisadvantage that it is not suitable for electrodes formed of flat sheetmetal, because it would change from a continuous stream that applies thefluid anti-wetting agent to the sheet material into a spraying of theanti-wetting agent. As a result, the process becomes uncontrollable.

[0007] Furthermore, the known method for applying a fluid anti-wettingagent has the disadvantage that a measure of the applied anti-wettingagent and thus the volume and/or the space requirement of theanti-wetting barrier are both very difficult and nearly impossible tocontrol and to reproduce. Anti-wetting barriers, produced in this way,usually exhibit a width of 500-1000 μm and a height of >10 μm. Onaccount of this, a higher space requirement for the anti-wetting barrierdevelops by which the storage utilization of the electrolyte condenseris negatively influenced.

[0008] Besides, in order to prevent the fluid anti-wetting agent frombeing absorbed by the porous anode body, it is necessary, with the knownmethod, to include a large secured space for the anode body, throughwhich the necessary area becomes still larger and the storageutilization decreases further. This is because a connection can bewelded for further contact with the anode only behind the relativelythick anti-wetting barrier.

[0009] The appearance of a protective ring of Teflon is technicallydifficult to achieve with electrodes in the form of a flat sheet metalbecause an oblong slit in the protective ring is necessary.

[0010] It is therefore the goal of the present invention to provide amethod for producing an anti-wetting barrier, in which the anti-wettingbarrier has a very small size.

[0011] The goal, according to the invention, is achieved by a methodaccording to claim 1. Advantageous implementations of the invention areincluded in the following claims.

[0012] The invention provides a method for producing an anti-wettingbarrier, in which the anti-wetting barrier is produced for an electrodethat is connected to the anode body of an electrolyte condenser. A fluidanti-wetting agent is applied to the electrode with droplets. Thespatial distance of the drops on the electrode is selected so that afterdropping the anti-wetting agent, an anti-wetting barrier develops as acontinuous line.

[0013] The method, according to the invention, has the advantage that ahigher precision barrier is possible by forming the anti-wetting barrierwith single droplets. This is due to the placement and spatial expansionof the anti-wetting barrier. In particular, the method, according to theinvention, makes it possible to attach the anti-wetting barrier veryclosely to the anode body. Furthermore, the method, according to theinvention, makes producing an anti-wetting barrier with a smallthickness and a small width possible such that the storage capacity ofthe electrolyte condenser is improved.

[0014] It is therefore advantageous to produce an anti-wetting barrier,the thickness of which is smaller than 5 μm. An anti-wetting barrierwith this thickness is sufficient to prevent wetting of the electrode.Furthermore, such an anti-wetting barrier is also suitable for breakingup during a welding process so that welding a connection onto theelectrode for positioning the anti-wetting barrier is possible. Withthis, the storage capacity of the electrolyte condenser produced by themethod according to the invention is improved.

[0015] The width and the thickness of the anti-wetting barrier appliedvia the drops can be influenced by the volume of the drops, as well asby their viscosity and surface tension. Choosing a small volume of dropsbetween 30 and 500 pl can ensure that the number of drops striking theelectrode for dissolution does not exceed a maximum for covered surfacesof the electrode. Choosing an attainably low viscosity can ensure thatthe drops dissolve when applied to the electrode, and they thereforespread over a large surface area that corresponds to the drop diameterfor the electrode. The development of a thin anti-wetting barrier canthus be obtained.

[0016] Furthermore, the anti-wetting barrier developed with regard toits thickness can be influenced by the surface tension of the drops. Byadding to the surface tension with dissolving means, surfactant in thisinstance, dissolution of the drops applied to the electrode can beachieved. Here, producing an anti-wetting barrier with a small thicknesshas again been supported.

[0017] It is furthermore advantageous to produce an anti-wetting barrierwith a width of less than 500 μm. Such an anti-wetting barrier has theadvantage that it occupies less space, thereby improving the storagecapacity of the electrolyte condenser.

[0018] Furthermore, the invention provides an anode of the electrolytecondenser with an anode body that is connected to an electrode in whichan anti-wetting barrier is applied to the electrode in the form of acontinuous line from anti-wetting agent, and in which the anti-wettingbarrier has a thickness of less than 5 μm.

[0019] Furthermore, it is advantageous to apply the drops onto theelectrode using a capillary tube. The use of a capillary tube makespossible precise application of drops on the electrode. This improvesthe reproducibility of the method and, at the same time, narrows theanti-wetting barrier. The drops develop by pressing the anti-wettingagent through the capillary tube.

[0020] Beyond that, it is advantageous to accomplish applying the dropsto the electrode without contact, which means without contact betweenthe capillary tube and the electrode. To do this, a very small amount ofliquid can be applied to the electrode without the danger of mixing theliquid applied to the electrode by the capillary tube. A suitabledistance between the capillary tube and the electrode is between 1 and 5μm.

[0021] In particular, droplets at a drop volume between 30 and 500 plcan create a correspondingly narrow and thin anti-wetting barrier forthe electrode. The method, according to the invention, therefore has theadvantage that the need for anti-wetting agent can be kept very small.

[0022] Furthermore, it is advantageous to use an electrode that exhibitsat least a level surface of sides for producing the anti-wettingbarrier. Such an electrode, in this case two-dimensional electrodescomprised of metal, can be provided via the method according to theinvention. Producing an anti-wetting barrier for such electrodes wouldbe possible via the known blasting procedure, as is described above,only when a large area is supplied.

[0023] The method, according to the invention, applies even to anodes,the electrodes of which have a round or oval cross-section and no levelsurface of sides.

[0024] In an advantageous implementation of the invention, a Teflonsuspension can be used for the anti-wetting agent. Such a Teflonsuspension has the advantage that it is liquid on either side and, onaccount of this, permits build-up of droplets. In anotherimplementation, the invention contains Teflon, which is a highlysuitable material for an anti-wetting barrier.

[0025] Through simple drying-out of the Teflon suspension, a firmanti-wetting barrier can be achieved by the droplets applied to theelectrode. As an anti-wetting agent, however, silicon or anothersuitable material could also be used.

[0026] In the following, the invention has been described in more detailaccording to examples of implementations and the figures correspondingto them.

[0027]FIG. 1 shows, as an example, a plan view of the anode of anelectrolyte condenser, in which an anti-wetting barrier has beenproduced on the electrode via the method according to the invention.

[0028]FIG. 2A shows, as an example, a schematic plan view of the anodeof a wider electrolyte condenser, in which the anti-wetting barrier hasbeen produced via the method according to the invention.

[0029]FIG. 2B shows an anode, according to FIG. 2A, from a side view.

[0030]FIG. 2C shows an anode, according to FIG. 2B, with only one sideof the anode body set up.

[0031]FIG. 3A shows, in this example, an anode with an electrode formedby a round wire, in which the anti-wetting barrier has been applied viathe method according to the invention.

[0032]FIG. 3B shows an anode, according to FIG. 3A, from a side view.

[0033]FIG. 4 shows, this example, application of the anti-wettingbarrier to the electrode via a capillary tube.

[0034]FIG. 1 shows the anode of an electrolyte condenser that includesan electrode 2, the final section of which is covered by an anode body3. Near the anode body 3, the electrode 2 has an anti-wetting barrier 1that is produced by applying drops 4 at a suitable spatial distance dfrom one another. The distance d of the drops 4 is selected so that ananti-wetting barrier 1 develops in the form of a continuous line. Theanode body 3 is produced by re-pressing the electrode 2 with a powder.

[0035]FIG. 2A shows the anode of an electrolyte condenser with an anodebody 3 that, in this case, can be a porous tantalum sinter body. Theanode body 3 is connected to an electrode 2 that contacts an anode body3. An anti-wetting barrier 1 is arranged closely above the anode body 3,which had been produced via the method according to the invention, inaccordance with FIG. 1 and which has the width b. The anode body 3 isproduced by pressing the electrode 2 with a paste.

[0036]FIG. 2A shows the anode of an electrolyte condenser with atwo-dimensional electrode 2 that is also known by the name, anodediverter. A two-dimensional electrode 2 makes possible electrolytecondensers with improved electrical characteristics.

[0037]FIG. 2B shows the subject of FIG. 2A from a side view. Accordingto FIG. 2B, an anode body 3 is set up on one side of the electrode andthe anti-wetting barrier exhibits a thickness D in each case. The anodebody 2 is produced by pressing on both sides of the electrode 2 with apaste.

[0038] The anode according to FIG. 2C, in contrast to the anode depictedin FIG. 2B, exhibits only an anode body 3 on one side of the electrode2. The anode body is produced by pressing on one side of the electrode 2with a paste.

[0039]FIG. 3A shows an electrolyte condenser, the electrode 2 of whichdoes not exhibit the form of flat metal, as shown in the FIGS. 2A thru2C, but instead is in the form of a round wire. Additionally, with suchan electrode, the method, according to the invention, can beadvantageously used for application of anti-wetting barrier 1.

[0040]FIG. 3B shows the subject of FIG. 3A from a side view.

[0041]FIG. 4 shows the production of anti-wetting barrier 1 viacapillary tube 5. A fluid anti-wetting agent is pressed by the capillarytube 5. Therefore, in this case, a Teflon suspension, which is thinnedwith water, can be used. In this case, the product with the name,“Topcoat Clear 852-200,” by the Dupont Company comes to mind for theTeflon suspension. To be suitable, a thinning of the suspension has beenachieved with 10 to 40 water parts by weight. Such a thinning has aviscosity of less than 10 mPas at room temperature. The anti-wettingagent can be applied with the help of a piezoactuator such as, forexample, the one by the name of “Microdrop” that is available from theMicrodrop Company, Corporation for Micro-proportion Systems, Ltd. Theanti-wetting agent is applied to the electrode 2 with drops and withoutcontact. The spatial distance between the drops 4 is so selected that ananti-wetting barrier 1 develops as a continuous line.

[0042] With the help of the capillary tube with, as an example, a nozzlediameter between 30 and 100 μm, the drops are produced with a volumebetween 30 and 500 pl.

[0043] The FIGS. 2A and 2B and/or 3A and 3B show that the anti-wettingbarrier has been applied as a closed ring around the electrode 2 that isan advantageous implementation of the invention. With this, wetting ofthe electrode 2 can be effectively prevented.

[0044] The production method, according to the invention, is not limitedto the tantalum condensers described here, but instead may also be usedentirely for the general production of condensers from other materialsas appropriate, and independently for production of the electrode andthe sinter body.

[0045] Producing an electrolyte condenser up until the production stepof applying anti-wetting barrier is described in the following using atantalum electrolyte condenser as an example.

[0046] Tantalum powder is applied to one or both sides of atwo-dimensional anode diverter as a paste, which, in this case, can be ametal, by means of (silk-) screen printing or stencil printing methods.Likewise, a two-dimensional or a wire-formed anode diverter can bepressed. Afterward, the anode is sintered in a vacuum at a hightemperature. A thin layer of tantalum pentoxide is produced from thetantalum by anode oxidation on the surface of the porous sinter body.This thin layer of tantalum pentoxide corresponds to the dielectriclayer of the condenser.

[0047] In this case, the method, according to the invention, forproducing an anti-wetting barrier for the anode diverter, can be used atthis point of the procedure. The method can, however, also be used priorto anode oxidation.

[0048] Further steps of the method for producing, e.g., tantalumcondensers, after application of the anti-wetting barrier are describedin the following:

[0049] From repeated dipping into manganese nitrate with subsequentthermal decomposition of the anode equipped with an anti-wettingbarrier, a layer of manganese dioxide develops on the surface of theporous sinter body. Correspondingly, outer contact layers are produce bydipping into graphite and silver conductive paint.

[0050] A cathode diverter in the form of a metal can now be glued to theouter contact layer, through which the prefabrication of a tantalumelectrolyte condenser is secured.

[0051] The invention is not limited to the above described examples butinstead is defined in its general form by claim 1.

1. Method for producing an anti-wetting barrier (1) on an electrode (2)that is connected to the anode body (3) of an electrolyte condenser,with which a fluid anti-wetting agent has been applied to the electrode(2) with drops and with which the spatial distance (d) of the drops (4)on the electrode (2) has been so selected that an anti-wetting barrier(1) in the form of a continuous line develops after the drying of theanti-wetting agent.
 2. Method according to claim 1, with which ananti-wetting barrier (1) has been produced with a thickness (D) of lessthan 5 μm.
 3. Method according to one of the claims 1 or 2, with whichan anti-wetting barrier (1) has been produced with a broadness (b) ofless than 500 μm.
 4. Method according to one of the claims 1 thru 3,with which the drops (4) have been produced by the pressing of theanti-wetting agent through a capillary tube (5).
 5. Method according toclaim 4, with which the application of the drops (4) takes place withoutcontact between the capillary tube (5) and the electrode (2).
 6. Methodaccording to one of the claims 1 thru 5, with which the drops (4) havebeen used with a volume between 30 and 500 pl.
 7. Method according toone of the claims 1 thru 6, with which an electrode (2) has been usedwith at least on level side surface.
 8. Method according to one of theclaims 1 thru 7, with which a Teflon suspension has been used as a fluidanti-wetting agent.
 9. Method according to one of the claims 1 thru 8,with which a fluid anti-wetting agent has been used, the viscosity ofwhich is smaller than 10 mPas.
 10. Anode for an electrolyte condenserwith an anode body (3) that is connected to an electrode (2), at whichan anti-wetting barrier (1) in the form of a continuous line from ananti-wetting agent has been applied to the electrode and at which theanti-wetting barrier (1) exhibits a thickness (D) of less than 5 μm.